The present invention relates to copper-based alloys for use in electronics for the manufacture of supports for components.
Copper, which, as is well known, is an excellent conductor of electricity, is used in many applications, especially in electronics; it is used as a support for electronic circuit components (lead frame) for the most varied components and especially electronic chips. In the production of circuits, the components are generally brazed, adhesively bonded and/or crimped and then hot-coated with plastics material on the copper support which must thus be temperature-resistant and preserve its mechanical characteristics.
Owing to this temperature resistance (restoration strength), copper-based alloys have been used; that enables the restoration strength to be increased while preserving a good conductivity.
The temperature strength, or what is referred to as restoration strength, corresponds to a mechanism leading to the softening of the copper alloy by activation of dislocation annihilation by re-heating to a high temperature. Restoration resistance is characterised by the maximum duration (for example longer than 10 minutes) of maintenance at an elevated temperature (for example 450.degree. C.) after which the hardness of the metal remains higher than a predetermined value.
The measured conductivity of the alloy, given as a percentage, corresponds to the 100% conductivity of pure copper. This percentage conductivity is called IACS conductivity.
By way of example, the alloy Cu Sn 0.15, which is an alloy of copper and tin, is used.
The copper supports used in electronics must not only offer good mechanical strength and good temperature strength but they must also exhibit excellent solderability and/or brazing suitability; to that end, the copper alloy is coated with a layer of nickel. This layer of nickel is applied to the alloy before cutting the products, such as supports. This results in a substantial amount of nickel-coated copper alloy waste, which is expensive to recover because it is necessary to use electrolysis to separate the copper from the nickel and to recover it.